High angular resolution cathode ray tube with sectorlike electrodes having different secondary emission areas



June 11. 1968 G. R. SPENCER HIGH ANGULAR RESOLUTION CATHODE RAY TUBE WITH SECTORLIKE ELECTRODES HAVING DIFFERENT SECONDARY EMISSION AREAS Filed Dec. 1. 1966 l/VVE/VTDR GORDON R. SPENCER 1 5 r I f 4r ORA/7 United States Patent 3,388,276 HIGH ANGULAR RESOLUTION CATHODE RAY TUBE WITH SECTORLIKE ELEC- TRODES HAVING DIFFERENT SECOND- ARY EMISSION AREAS Gordon R. Spencer, Westwood, Mass., assignor to Raytheon Company, Lexington, Mass., a corporation of Delaware Filed Dec. 1, 1965, Ser. No. 598,492 Claims. (Cl. 31368) ABSTRACT OF THE DISCLOSURE A cathode ray tube comprising a segmented metal target having a plurality of sectors, each sector being divided into at least two areas having different secondary emission ratios, 21 lead connected to each sector, an electron gun for directing an electrom beam onto the target and deflection plates positioned between the target and the electron gun for deflecting the beam to a selected sector of the target and onto a selected areaof the selected sector.

BACKGROUND OF THE INVENTION In many applications employing a cathode ray tube, it is desirable to have high angular resolution. Some prior art cathode ray tubes are provided with segmented targets for increasing the angular resolution. However, in some situations, the angular resolution provided by the prior art segmented targets is not adequate for the accuracies required. The present invention provides a greater angular resolution than that afforded in prior art devices.

SUMMARY OF THE INVENTION The present invention includes a cathode ray tube for use in high angular resolution applications comprising a segmented target having a plurality of sectors, each sector being divided into at least two areas having different secondary emission ratios; a lead connected to each sector; means for producing an electron beam; and means positioned between the target and the beam-producing means for deflecting the beam to a selected sector of the target, whereby a response on any one lead indicates that the electron beam is striking the sector to which that lead is connected and the level of such response indicates which area of the sector is being bombarded. This invention could be employed in sonar applications requiring precision bearing resolution and in numerical machine tool, control systems requiring accurate angular resolution for movement of machine parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cathode ray tube embodying the present invention;

FIG. 2 shows the segmented target employed in the cathode ray tube shown in FIG. 1; and

FIG. 3 illustrates an alternative embodiment of the target shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to the drawing wherein like characters of reference designate like parts throughout the several views, FIG. 1 shows a cathode ray tube 10 embodying the present invention. The cathode ray tube 10 may be among the class of cathode ray tubes having segmented metal targets with a plurality of connectors afiixed to the target, such as the Raytheon radial resolution tube, type CK1378. In general, such cathode ray tubes are used for commutating, switching or angular resolution applications, wherein the particular combination of input signals to the deflection plates determines which target segment is bombarded by the electron beam. The CK1378 is used in angular resolution applications to resolve the approximate direction of a signal which is received by sensors having their axes of peak sensitivity directed at right angles to each other. The resolution required of the device depends upon the particular application.

The cathode ray tube 10 includes a glass envelope 12 or similar transparent material. Envelope 12 comprises a main body portion having a relatively slender neck portion 14. The neck portion 14 contains an electron gun 16 which may be of any conventional type and which may be connected by suitable externally extending leads 18 to suitable sources of electrical potentials whereby the gun may be operated to produce a beam of electrons which is directed into the main body of the envelope 12. Positioned adjacent the electron gun 16 are two pairs of deflection plates 20 and 22 having leads 24 and 26 respectively connected thereto. The plates 20 are horizontal deflection plates and the plates 22 are vertical deflection plates. The leads 24 and 26 are provided to connect the deflection plates 29 and 22 to suitable external sources of potential. Spaced from the deflection plates 20 and 22 in the widened portion of the envelope 12 is a conductive coating 25 on the inner surface of the envelope. A lead 27 contacts the coating 25 and projects through the envelope and is for connection to a suitable source of positive potential. The coating 25 may be made of graphite or other similar material.

The envelope 12 terminates at the end opposite the leads 18 with a glass face 28. Positioned inside the envelope 12 next to the glass face 28 is a segmented metal target 30 having a plurality of sectors 32. The target 30 shown in FIG. 1 is divided into 36 sectors of equal size which are arranged in a circle. Connected to each sector 32 of the target 30 is a lead 34 which extends from the target 30 through the glass face 28 and projects outside the envelope 12. Having 36 sectors, the target 30 provides an angular resolution of one part in 36 or an angle of 10. The coating 25 is charged with a positive potential placed on lead 27 which is more positive than the target 30.

FIG. 2 shows an end view of the target 30 shown in FIG. 1. Each sector 32 of the target 30 is divided into two equal areas, 36 and 38. Each area 38 of the sectors 32 constitutes the clockwise half of each sector 32, while each area 36 of the sectors 32 constitutes the counterclockwise half of a sector 32. The areas 36 are each coated with aluminum which has one secondary emission ratio. The other areas 38 of each sector 32 are coated with magnesium which has a different secondary emission ratio from that of aluminum.

Connected to each sector 32 is a lead 34 which provides a connection to the sectors for determining any output response which may occur on any lead 34. Each lead 34 may 'be connected anywhere on each sector 32 even though for purposes of description, each lead 34 is shown connected to the intersection between the clockwise and counterclockwise halves of each sector 32. The sectors 32 are physically insulated from one another so that no electrical contact exists bet-ween the sectors. An insulator such as mica may be used to provide the necessary insulation. The sectors 32 may be arranged in a flat circular pattern as shown in FIG. 2 or may be arranged in a circular pattern just slightly overlapping one another. If adjacent sectors do not overlap, they should be spaced closer than the 'width of the electron beam.

The output current is determined by the equation:

out= p( where I is the output current appearing on any lead 34, I is the primary current striking the target and 0' is the Patented June 11, 1968 secondary emission ratio of the particular material. for most materials will be between 1 and 5 and for purposes of the present invention, the secondary emission ratio must be different from unity because otherwise the output current will be zero.

The secondary emission ratio for aluminum with a thin surface oxide is approximately 3 while the secondary emission ratio for magnesium with a thin surface oxide is approximately 4. Although aluminum and magnesium have been employed as the coatings for each of the areas 36 and 38 of the sectors 32, other materials having different secondary emission ratios may be employed. In addition, although the target 30 has been shown as having 36 sectors, in practice the target could be constructed having any number of sectors as desired.

FIG. 3 shows a modification of the target shown in FIG. 2. The target 40 of FIG. 3 is divided into a plurality of equal sized sectors 42 arranged in a circle. A lead 43 is connected to each sector 42. Each sector 42 is divided respectively into three equal sized areas 44, 46 and 48 arranged in the same sequence on each sector 42. The area 44 of each sector 42 is coated with silver (twil /2 the area 46 is coated with aluminum (0%3), and the area 48 is coated with magnesium (d i). Each of the areas 44, 46 and 48 have different secondary emission ratios as indicated above. Although the materials silver, aluminum and magnesium have been used for the areas of the sectors 42 other materials having different secondary emission ratios from each other could be employed. As in FIG. 2, although the target 40 of FIG. 3 is made up of 36 sectors 42, any desired number of sectors could be constructed.

The operation of the cathode ray tube shown in FIG. 1 is such that when the electron gun 16 emits an electron beam, the beam will be deflected by plates and 22 and as a result will strike a particular sector 32 of the target shown in FIGS. 1 and 2. With the leads 34 connected to appropriate logic means (not shown), upon striking a particular sector 32, an output current would exist on the lead 34 connected to the sector 32 which was struck by the beam. The level of the output current existing on the lead 34 would indicate which of the two areasthe clockwise or the counterclockwise half-was struck by the electron beam. Thus, the logic means would include detection means having 3 levels of operation-no current, current representing one secondary emission ratio and another current representing another secondary emission ratio. If an output cur-rent appears on two adjacent leads, then the logic means would indicate that the beam is striking intersection of two of the sectors 32. By providing this segmented target having a plurality of sectors 32 and with each sector having at least two coatings of different secondary emission materials, high angular resolution may be achieved.

Certain modifications will appear to those skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the appended claims.

I claim:

1. A cathode ray tube for use in high angular resolution applications comprising:

a segmented target having a plurality of sectors, each sector being divided into at least two areas having different secondary emission ratios;

a lead connected to each sector;

means spaced from said target for producing an electron beam; and

means positioned between said target and said beam producing means for deflecting said beam to a selected sector of said target, whereby a response on any one lead indicates that the electron beam is striking the sector to which that lead is connected and the level of such response indicates which area of the sector is being bombarded.

2. A cathode ray tube as set forth in claim 1 wherein:

each of said sectors is divided into two equal sized areas having different secondary emission ratios.

3. A cathode ray tube as set forth in claim 1 wherein: each of said sectors is divided into three equal sized areas having dilferent secondary emission ratios.

4. A cathode ray tube for improving angular resolution of the tube comprising:

a segmented tar-get including a plurality of sectors;

an area of each sector coated with a material having one secondary emission ratio;

another area of each sector coated with a material having a diflerent secondary emission ratio from the other area;

a lead connected to each sector of said target;

an electron gun spaced from said target for bombarding said target with an electron beam; and

deflection plates positioned between said gun and said target for deflecting said beam to a selected sector of said target, whereby a response on any one lead indicates that the electron beam is striking the sector to which that lead is connected and the level of such response indicates which area of the sector is being bombarded.

5. A cathode ray tube as set forth in claim 4 wherein:

each sector is divided into two areas of equal size and one of said areas is coated with magnesium and the other of said areas is coated with aluminum.

6. A cathode ray tube as set forth in claim 5 wherein:

an electron beam striking a magnesium-coated area of a sector will yield a higher output than if the beam strikes an aluminum-coated area.

7. A cathode ray tube as set forth in claim 4 wherein:

said target is divided into 36 equal sized sectors arranged in a circle so that angular resolution is 10.

8. A cathode ray tube for improving angular resolution for use in angular resolution applications comprising:

a segmented metallic target made up of a plurality of sectors, said sectors arranged in a circle;

each sector being divided into two areas of equal size, one area being the clock-wise half and the other area being the counterclockwise half;

the clock-wise half of each sector made of a material having a selected secondary emission ratio;

the counterclockwise half of each sector made of another material having a diflerent secondary emission ratio from that of the material of each clockwise half;

a lead connected to each sector of said target for detecting any secondary emission from said sector;

an electron gun spaced from said target for bombarding said target with an electron beam; and

deflection plates positioned between said gun and said target for deflecting said beam to a selected sector of said target, whereby an output current on any one lead indicates that the electron beam is striking the sector to which that lead is connected and the level of the output current indicates which half of the sector is being bombarded.

9. A cathode ray tube as set forth in claim 8 wherein:

the clockwise half of each sector is coated with magnesium and the counterclockwise half is coated with aluminum,

10. A cathode ray tube as set forth in claim 8 wherein:

said target is divided into 36 equal sized sectors arranged in a circle so that angular resolution is 10.

References Cited UNITED STATES PATENTS 2,069,441 2/ 1937 Headrick 315-12 2,250,529 7/ 1941 Gray et a1 31368 2,465,380 3/1949 Labin et al 313-73 X 2 ,470,731 5/ 1949 Sziklai 329- 2,540,384 2/1951 Sears 313-68 X JAMES W. LAWRENCE, Primary Examiner. V. LAFRANCHI, Assistant Examiner. 

